Sealed off building drainage and vent system

ABSTRACT

A drainage and ventilation system for a building is provided which includes two or more stacks which communicate fluid therein. The stacks are connected to a sewer for discharging liquid thereto, with at least one of the stacks having a discharge source for delivering liquid to a wet stack portion of that stack. A trap is positioned between the wet stack portion and the discharge source for inhibiting the passage of gas therethrough. The stacks are interconnected at an upper end thereof by a connecting member such as a connecting pipe or manifold, whereby air may be communicated between the stacks. An air admittance valve and a positive air pressure attenuation device are located above the connecting member, whereby air may be introduced into the stacks to compensate for entrained air moving with the liquid into the sewer, and air may be accumulated during increased pressure events, both helping to preserve trap seal integrity without releasing foul air into the surrounding environment.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns building drainage and ventilation systemswherein air may be admitted into a ventilation system while avoiding thedischarge of air therefrom caused by positive air pressure transients inthe system. More particularly, it is concerned with a system whereby apositive air pressure attenuation device and an air admittance valve maybe employed in combination, and also a system including a plurality ofventilation conduits which are connected to one or more common ventpipes.

2. Description of the Prior Art

It is common for buildings to include plumbing systems which includeventilation stacks as a part of the drainage system. The drainagesystems lead to a sewer system, such as a municipal sewage system, acombined sanitary sewer and stormwater sewer system, or a septic tank,and as a consequence foul odors must be prevented from entering thebuilding from the sanitary sewer system. This is accomplished in largemeasure by the use of generally U-shaped water traps within the drainagesystem, whereby water held in the trap blocks the escape of foul airinto the building. It is important to maintain a sufficient quantity ofwater in the trap to avoid direct passage of the air in the drainagesystem into the environment of the building. It is thus desirable tocontrol pressure fluctuations within the drainage system and itsventilation system, including both overpressurization andunderpressurization.

Traditional modes of trap seal protection rely predominantly on passivesolutions where reliance is placed on cross-connections and verticalstacks vented to the atmosphere. This approach, while both proven andtraditional, has inherent weaknesses, including the remoteness of thevent terminations and the multiplicity of open roof level stackterminations inherent in complex buildings such as buildings havingmultiple tenants. The complexity of the vent system required also hassignificant cost and space implications. Moreover, air transientgradients generated within the building drainage and ventilation systemas a natural consequence of system operation may be responsible for trapseal depletion and contamination of habitable space within the building.

The development of air admittance valves (AAVs), such as is shown byU.S. Pat. No. 6,532,988 and companion International ApplicationPublication No. WO 00/46454, the disclosure of which is incorporatedherein by reference, provides the designer of drainage and ventilationsystems with a means of alleviating negative transients generated asrandom appliance discharges contribute to the time dependent water-flowconditions within the system. AAVs are one active control solution tothe problem presented by the need to allow air to enter into thedrainage system freely but inhibit the release of foul air from thedrainage system into the atmosphere. However, these AAVs also preventpositive air transients which arise within the drainage system fromescaping to the atmosphere, which in consequence leads to a reducedperformance of the drainage system. The positive air pressure transientpropagation within the building drainage and ventilation system as aresult of intermittent closure of the free airpath through the system orthe arrival of positive transients generated remotely within the sewersystem, such as possibly by some surcharge event downstream includingsurcharges caused by heavy rainfall in combined sewer applications, isnot addressed by AAVs.

It is also known to have address positive air transients by theemployment of a positive air pressure attenuation device (PAPA). PAPAs,such as disclosed in published International Application No. WO03/021049, the disclosure of which is incorporated herein by reference,may include a variable volume bag that expands under the influence of apositive transient and therefore allows system airflows to attenuategradually, therefore reducing the level of positive air transientsgenerated in the system.

SUMMARY OF THE INVENTION

The present invention is directed to a complete building drainage andventilation system which combine the advantages of each of the foregoingdevices to provide greater protection against the introduction ofdiseases such as SARS or terrorist attack by the introduction ofbiological or chemical agents. Moreover, the present invention includesa system whereby in a complex or multi-tenant building, multipledrainage and ventilation systems may be interconnected at the upperlevel of the system into a common discharge stack, thereby offering acompletely closed-off drainage system providing a maximum of protectionagainst the introduction of infectious biological disease or chemical orbiological attack, save for that limited amount of air which may enterthrough the AAV during a limited period of system underpressure.

The drainage and ventilation system hereof preferably includes abuilding having a plurality of stacks each having drainage pipes whichare interconnected to one or more common ventilation pipes, andincluding the use of both a PAPA and an AAV which are in fluidiccommunication with the stacks and function as a part of the system. ThePAPA and AAV may be positioned at various locations of the system, suchas, for example, local devices positioned in fluidic communication withthe pipes of the system at sensitive areas of the system, positioningPAPAs at a lower area of the stack by use of a diversion pipe,positioning one or multiple AAVs at or adjacent water traps in thepipes, or by providing a PAPA and an AAV in fluidic connection at theupper end of the system so as to be in fluidic communication with aplurality of stacks. This latter approach, as may be seen in thefollowing description, provides a simple and elegant solution whichutilizes the fluidic communication between the stacks when connected tocommon ventilation pipes in combination with the PAPA and AAV to addresspressure fluctuations throughout the system. The building may be abuilding of the type wherein the intrusion of outside agents, odors andthe like are controlled and or limited in their ability to reach atleast certain rooms within the building. As used in the descriptionhereof, the stacks include, in addition to the drainage pipes, watersources such as drains, sinks, toilets, water closets and the like whichpermit water to enter the drainage pipes, and each such water source isfluidically connected to the associated drainage pipe via water traps orequivalent devices which permit the flow of water through the drainagesystem but inhibit the escape of odors and agents from the drainagesystem to the water sources. The combined usage of the PAPA and AAV insuch a system provides a closed-off drainage system offering a maximumof protection against the intrusion of infections, biologicalcontaminants, and chemical agents into a secured building by limitingthe introduction of air into the system through the AAV. The combineduse of the PAPA and AAV protects the water traps or equivalent devicesagainst either underpressure conditions by the use of the AAV, and alsooverpressurization by the use of the PAPA, which could otherwise occurin the system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a sealed building drainage and ventilationsystem in accordance with the present invention, showing a buildingarrangement having four stacks each with a respective water source whichis connected to respective drain and ventilation pipes, and having acommon ventilation pipe provided with a PAPA and an AAV in a T orparallel arrangement;

FIG. 2 is a schematic view of a sealed building drainage and ventilationsystem similar to that shown in FIG. 1, but having the PAPA and AAVconnected in series with the AAV positioned remotely relative to thePAPA;

FIG. 3 is an exploded view of an AAV useful in accordance with thepresent invention;

FIG. 4 is a vertical sectional view of a PAPA useful in accordance withthe present invention;

FIG. 5 is a graph illustrating water closet discharges showing flow rateover time in a test system according to FIG. 1;

FIG. 6 is a graph illustrating entrained airflow rates over time inannular water flows through a test system according to FIG. 1;

FIG. 7 is a graph illustrating stack height versus stack air pressure ina test system according to FIG. 1;

FIG. 8 is a graph illustrating the relationship of air pressure withindrainage pipes time over time during water closet discharges in a testsystem according to FIG. 1;

FIG. 9 is a graph showing air pressure profiles comparing stack heightto stack air pressure from the base of a stack to the common pipeleading to the AAV and PAPA during an initial phase of a water closetdischarge as shown in FIG. 8;

FIG. 10 is a graph similar to the graph of FIG. 9 showing air pressureprofiles comparing stack height to stack air pressure from the base of astack to the common pipe leading to the AAV and PAPA during a laterphase of a water closet discharge as shown in FIG. 8;

FIG. 11 is a graph showing air pressure over time during sequentiallyapplied sewer air pressure transients imposed at the base of each stackin a test system according to FIG. 1;

FIG. 12 is a graph showing entrained airflows in the respective stacksduring the sequentially applied sewer air pressure transients shown inFIG. 11;

FIG. 13 is a graph illustrating the stack air pressure at variousheights of two of the stacks of the test system according to FIG. 1 at15 seconds into the application of the sewer air pressure transients ofFIG. 11;

FIG. 14 is a graph showing PAPA volume and AAV airflow over time duringthe applied sewer air pressure transients imposed at the base of eachstack as shown in FIG. 11;

FIG. 15 is a graph showing trap seal water levels in pipe 2 of stack 1during a surcharge event and subsequent sewer transient in a test systemaccording to FIG. 1;

FIG. 16 is a graph showing trap seal water levels in pipe 7 of stack 2during a surcharge event and subsequent sewer transient in a test systemaccording to FIG. 1;

FIG. 17 is a graph showing trap seal water levels in pipe 15 of stack 3during a surcharge event and subsequent sewer transient in a test systemaccording to FIG. 1;

FIG. 18 is a graph showing trap seal water levels in pipe 20 of stack 4during a surcharge event and subsequent sewer transient in a test systemaccording to FIG. 1; and

FIG. 19 is a graph showing trap seal water retention in pipes 2, 7, 15and 20 following a surcharge to the network and subsequent sewer imposedtransient in a test system according to FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In connection with the above-referenced invention, a building 30 isschematically shown in FIG. 1 which includes a sealed off drainage andventilation network or system 32 as typically used in for handling anddischarging water in a plumbing system. The system 32 is vented to thesurrounding atmosphere and liquid or liquid/solid discharges from thesystem 32 are illustrated as being delivered to a sewer 34, which asused herein includes not only a municipal sewage system but septic tanksystems and the like as is well known to those skilled in the art. Thebuilding 30 as illustrated includes a simplified plumbing arrangementserving four individual compartments 36, 38, 40 and 42, but is to beappreciated that the showing of four compartments is merely illustrativeof buildings having multiple compartments however denominated such asoffices, rooms or apartments. While in the illustration of FIGS. 1 and2, the individual compartments 38 and 40 are shown as being at a higherlevel than the compartments 36 and 42, the system hereof is not limitedto multiple level compartments and with respect to the example describedhereinafter, this is for convenience of illustration only. In theexample described hereinafter, all of the compartments and theirrespective components (dry stack pipes, feed pipes, discharge sources,traps, dead end pipes, wet stack pipes, and the like) are actuallylocated at substantially the same relative elevation, i.e. that alltraps are at substantially the same elevation, all dead end pipes are atsubstantially the same elevation, and so on.

To assist in further understanding of the present invention, FIG. 1illustrates a simplified system 32 having four stacks A, B, C and D. Thefour stacks are linked or fluidically interconnected at an upper levelwithin or outside the structure by a suitable junction, here shown as acommon pipe or manifold 11. As used herein, the stacks each have wetstack portions which include discharge pipes and feed pipes, and drystack portions which do not typically come into contact with liquid.These portions may be part of a continuous pipe, but more typically andfor ease of understanding in the example, the description of the system32 hereof refers to pipes which are fluidically interconnected as partof a stack. Thus, the wet stack portion of the four stacks A, B, C and Dhave respective wet stack discharge pipes 1, 6, 14 and 19 which deliverdischarges from the system to the sewer 34, and feed pipes 2, 7, 15 and20 which deliver water to the wet stack discharge pipes 1, 6, 14 and 19respectively from respective discharge sources 46, 48, 50 and 52. Thefeed pipes 2, 7, 15 and 20 each include respective U-shaped traps 54,56, 58 and 60. The discharge sources 46, 48, 50 and 52 are also referredto herein as “appliances” and are illustrated as water closets, alsoknown as toilets or commodes, but it may be appreciated that thesesources may include a variety of plumbing hardware or fitting items,such as by way of example but not limitation, floor drains, sinks,shower stalls, bidets, water fountains or the like. Each stack A, B, Cand D further includes wet stack upper pipes 3, 8, 16 and 21 which arelocated just above the junctions where the feed pipes connect to thestacks, dead end pipes 4, 9, 17 and 22, and upper pipes 5, 10, 18 and23. The wet stack upper pipes and the dead end pipes are consideredherein as part of the wet stack portion of the stacks, and the upperpipes 5, 10, 18 and 23 are considered dry stack pipes, meaning thattypically only air and not liquid is typically held therein andcommunicated therethrough. The upper or dry stack pipes may be directlyor indirectly fluidically coupled for connecting each of the respectivestacks A, B, C, and D at an upper level, i.e. above the respective deadend pipes. While such connection means may be a direct connection of onedry stack pipe to another, more typically an interconnecting member isused to fluidically connect the stacks at an upper level. Such aninterconnecting member or means may be a pipe, hose or fitting, and ishere illustrated as a common pipe or manifold 11 which fluidicallyconnects the stacks and extends upwardly for connection to otherconnectors for ventilation. In the illustration of the system shown inFIGS. 1 and 2, the common pipe 11 in turn is connected at its uppermostend to a T fitting 62 which connects to PAPA pipe 13 and AAV pipe 12. APAPA 68 is then connected to the terminal end of the PAPA pipe 13 and anAAV 70 is then connected to the AAV pipe 12. Because both the AAV andPAPA are designed to be positioned either within the ambient atmosphereor within a closed environment, the T fitting 62 and the pipes 12 and 13may be located above the roof 72 of the building 30. Thus, in the system32 of FIG. 1, the T fitting 62 provides that the PAPA 68 and the AAV 70are connected in parallel. While the positioning of the PAPA 68 and theAAV 70 at the upper end of the system 32 is a preferred arrangement ofthese components, it is to be understood that the invention hereofcontemplates other placement options for the PAPA 68 and AAV 70 withinthe system 32. For example, one or a plurality of the AAVs 70 may belocated at alternate locations such as adjacent and fluidicallyconnected to the traps 54, 58, 60 and 62, or one or more PAPAs could beinstalled proximate the stacks A, B, C and D by the use of a diversionpipe fluidically connected to the stack, including positioning thediversion pipe for connection to the wet stack portion. Positioning thePAPA 68 and the AAV 70 at these alternate locations within the building30 would still fulfill the goal of providing air to the system 32 fromcontrolled sources.

FIG. 2 shows an alternate configuration of the system 32A which issimilar to the system 32 in most respects, and in which similarreference characters are used to identify similar components. In thesystem 32A, however, the T fitting 62 is removed and the PAPA 68 isconnected either directly to the common pipe 11 or by a further pipe orthe like. A connector pipe 74 is then provided between the PAPA 68 andthe AAV 70 which, as in system 32, is able to receive air from theambient atmosphere or, as illustrated, from an accessible loft space toprovide an enclosed, sealed building source of air to the AAV 70.

One AAV 70 useful in accordance with the present invention is shown inU.S. Pat. No. 6,532,988, the disclosure of which is incorporated hereinby reference and shown in an exploded view in FIG. 3. Such an AAVbroadly includes a valve body 76 having a lower part comprising anormally vertical tubular member 78 adapted to be connected to a pipeincluding a common pipe or manifold as described above which is part ofa sanitary discharge and ventilation system. The upper end of thetubular member 78 has a conical shaped restriction 80 which is closed atits extremity. The conical upper portion 80 of the tubular member 78 isprovided with two diametrically opposed passages 82 each of which has amoulded-in grid 84 to prevent the entry of strange objects, such asanimals or insects. The conical upper portion 80 of the tubular member78 is surrounded by an oblong bowl-shaped housing 88, extending upwardsfrom the tubular element 78 and having an upper edge 90 which issituated about a horizontal plane crossing the upper extremity of theconical portion 80 of the tubular member 78.

The space between the bowl-shaped housing 88 and the conical portion 80of the tubular member is subdivided by a partition 92 into mutuallyopposed orthogonally arranged pairs of first and second chambers. Thefirst pair of chambers are delimited by the partition 92 and closedsections 94 of the conical portion 80 and are in communication with thesurrounding atmosphere via openings 96 in the bowl-shaped housing 88.The second pair of chambers are delimited by the partition 92 and thebowl-shaped housing 88 and are in communication with the lower tubularmember 78 via the passages 82 in the conical portion 80 of the tubularmember 78. The upper edge of the partition 92 is located about thehorizontal plane and is configured so as to form a valve seat 98. Avalve member 100 is carried on the upper edge of the partition 92 and isnormally seated on the valve seat 98 to isolate the first pair ofchambers from the second pair of chambers when the internal pressure inthe system 32 (or 32A) is at least equal to the atmospheric pressure.

The valve member 100 is lifted or elevated above the valve seat 98 inresponse to a lowering of the internal pressure below the atmosphericpressure to thereby place the first pair of chambers in communicationwith the second pair of chambers, thus admitting atmospheric air intothe system 32, 32A connected to the lower tubular member 78. The valvemember 100 and the corresponding valve seat 98 preferably have abutterfly-shaped form which is positioned in a longitudinal directioninside the oblong bowl-shaped housing 88. The openings 96 in thebowl-shaped housing 88 are also provided with a grid 102 to avoidinterference between the valve member 100 with any foreign object. Theclosed extremity of the conical portion of the tubular member 78 isprovided with a closed cavity 104 extending downwards and being arrangedas a fixed female guiding means for the valve member 100 which is, forthat purpose, provided with a projection 106 (movable male guidingmember) having similar dimensions as the cavity 104. The main or innerpart of the valve member 100 is of hard plastic or the like, while theperipheral border part 108 is made of a soft plastic material to sealwith the valve seat 98. The valve body 76 is closed with an upper lid110 which encloses the upper edge in a tight manner by slightly conicalnormally downwardly extending side walls 112.

An example of a PAPA 68 useful in accordance with the present inventionis shown in International Application PCT/IB02/03577 published asInternational Publication Number WO 03/021049 published 13 Mar. 2003,incorporated by reference and in a corresponding national stage U.S.patent application Ser. No. 10/588,420 filed Aug. 16, 2004 and publishedon Dec. 30, 2004 as Patent Publication No. 20040261870, the disclosureof which is incorporated by reference herein. Such a PAPA 68 comprisesan external casing 114, a housing 116, a flexible reservoir 118 and anend cap 120. The assembled PAPA 68 is shown in FIG. 4. The flexiblereservoir 118 covers the central portion of the housing and is securedto a housing receiving end 122 and the housing remote end 124 by meansof an “0” ring 126. The flexible reservoir 118 is sealed against thehousing receiving end 122 and the housing remote end 124 by the “0” ring126 compressing a layer of sealant (not shown). This allows the flexiblereservoir 118 to operate without any leakage.

The housing receiving end 122 and the housing remote end 124 are linkedtogether by means of separator plates 128 leaving between them openspaces in contact with the flexible reservoir 118.

The external casing 114 fits partly over the housing 116 and over theflexible reservoir 118. The external casing 114 has a plurality of meansof ventilation 130, such as openings, shown for example in FIG. 4 in abase surface 132. These means of ventilation 130 allow the flexiblereservoir 118 to be in permanent contact with the atmospheric air atatmospheric pressure whilst preventing the flexible reservoir 118 frombeing damaged by any external event. A graduated connector 134 may beprovided for attaching the PAPA 68 to, e.g., pipe 13, T-fitting 62, orcommon pipe 11 of a drainage and ventilation system 32 or 32A. Thegraduated connector 134 allows the connection of at least two differentsized pipes together in a secure manner, and may be made of anelastomeric material. The housing 116 includes a remote section 136which leads to the housing remote end 124, a receiving section 137 whichextends remotely from the housing receiving end 122, and the separatorplates 128 which allow airflow to continue through the PAPA when theflexible reservoir 118 is fully collapsed. The separator plates 128 donot extend fully around the circumference of the housing 116, but ratherprovide gaps 140 between the separator plates 128 allow air from thedrainage and ventilation system 32 or 32A to enter the flexiblereservoir 118 and inflate the latter in the case of positive pressurewithin the system 32 or 32A, thus absorbing the energy of any transientpressure wave. Two or more PAPAs 68 may be connected in series, with theconnections between the PAPAs 68, or between a PAPA 68 and an AAV 70, orto connecting pipes or other connectors, being a push fit connection.

In complex building drainage systems, the operation of the system isdesigned to accommodate the discharge of water into the system byvarious appliances such as the discharge sources 46, 48, 50 and 52.Multiple discharge sources are typically provided in a discharge networkor system, and their operation is almost always entirely random. As aconsequence, these discharge sources provide conditions which result inair entrainment and pressure transient propagation, which are entirelyrandom. No two systems will be identical in terms of their usage at anytime. This diversity of operation implies that inter-stack venting pathswill be established if the individual stacks within a complex buildingnetwork are themselves interconnected. The present invention takes intoaccount this diversity and utilizes it to provide system venting and asealed drainage and ventilation system 32 or 32A. While it iscontemplated that the best mode of operation of such a sealed drainageand ventilation system will employ the interconnection within the systemat a relatively upper location with respect to the building, which isthat sector of the system which would normally be considered the “drystack” region above water discharge sources, it may be possible toprovide the interconnection between the stacks of the system at a lowerlevel including the alternate positioning of the PAPA 68 and AAV 70 asdescribed above.

To provide a most preferable sealed building drainage and ventilationsystem 32 or 32A as illustrated herein, negative air transients in thesystem would be alleviated by drawing air into the network from a securespace providing either purified or segregated air, rather than from theexternal atmosphere. This may be provided by the use of AAVs 70positioned to deliver air to the system at locations adjacent thedischarge sources 46, 48, 50 and 52, or from a purifying mechanism, orat a predetermined location within the building, such as an accessibleloft space 142 as an alternative to being located in the ambientatmosphere above roof 72. Similarly, to provide such a preferable sealedbuilding drainage and ventilation system 32 or 32A, it is necessary toattenuate positive air pressure transients by means of PAPA devices 68mounted within the building envelope. While it might be considered thatthis would be problematic, positive air pressure could build within thePAPAs and therefore negate their ability to absorb the positive airpressure arising from transient airflows within the system. This problemis largely addressed in the present invention by linking generallyupright stacks in a complex building and thereby utilizing the diversityof use inherent in building drainage systems. Such diversity helps toensure that pressure transients delivered to PAPA devices 68 arethemselves alleviated by allowing trapped air to vent through theinterconnected stacks and downward into the sewer 34. The presentinvention also utilizes the complexity of the system 32 or 32A toprotect the system 32 or 32A from sewer driven overpressure and positivetransients. Typically, a complex building's drainage and ventilationsystem 32 or 32A will be interconnected to the main sewer 34 and itsinherent piping systems at least initially via a number of connectingsmaller bore drains. The larger bore size of the sewer 34 advantageouslyensures that adverse pressure conditions will thereby be distributedamong the stack piping and the network interconnection will continue toprovide venting routes.

EXAMPLE

The following example of the operation of the system 32 utilizes theAIRNET simulation developed through research at Heriot Watt University.The AIRNET simulation of system operation provides local air pressure,velocity and wave speed information throughout a network at time anddistance intervals as short as 0.001 seconds and 300 mm. In addition,the AIRNET simulation utilized in the example hereof replicates localappliance trap seal oscillations and the operation of active controldevices, thereby yielding data on network airflows and identifyingsystem failures and consequences. The example is illustrated withreference to system 32 as shown in FIG. 1 which illustrates a four stacknetwork. The four stacks A, B, C and D are fludically connected at ahigh level by common pipe 11 leading to the PAPA 68 and AAV 70. Waterdownflows in any stack generate negative transients which typicallydeflate the PAPA 68 and open the AAV 70 to provide an airflow into thesystem 32. Positive pressure generated by either stack surcharge (which,as used herein, includes introduction of liquid into a stack) or sewertransients (which, as used herein, involves increases or decreases inpressure arising from an event in the sewer such as fluid flow, a dropin liquid volume in the sewer, or an increase in liquid volume in thesewer) are attenuated by the PAPA and by the diversity of use thatallows one stack-to-sewer route to act as a relief route for fluid inother stacks.

In the example of the system 32 illustrated in FIG. 1, the overallheight of the system 32 from bases 150, 152, 154 and 156 of therespective stacks A, B, C and D to the PAPA 68 and AAV 70 is 12 meters.Each of the bases is preferably connected to the respective stackindependent of the connection between the other bases and the sewer.Pressure transients generated within the network will propagate at theacoustic velocity of air, i.e., 330 m/s. In the context of the system 32as illustrated herein, this implies pipe periods, which is the roundtrip travel time of a pressure transient from stack base to a PAPA 68 ofapproximately 0.08 seconds and from stack base to stack base ofapproximately 0.15 seconds.

In the example of the system 32, which is a simplified illustration of acomplex building drainage and ventilation system used in the examplehereof, no local trap seal protection is included, that is, while thetraps 54, 56, 58 and 60 in the present example do not have activetransient controls such as AAVs or PAPAs, such could be provided at thetraps. Traditional networks as known in the art could include passiveventing where separate vent stacks would be provided to the atmosphere.Also, as shown in FIG. 1, the bases 150, 152, 154 and 156 of therespective stacks A, B, C and D are ideally connected separately to thesewer 34 either directly or to separate connection drains so thatdiversity in the system 32 or 32A acts to aid in system self-venting. Ina complex building this arrangement would not be arduous and would inall probability be the norm.

In the present example, the pipes 1, 3, 6, 8, 14, 16, 19 and 21 are allconsidered wet stack pipes. Each of the pipes 1 through 10 and 11through 23 are 0.1 m in diameter, with pipes 1-4, 6-9, 14-17, and 19-22being 2 meters in length. Pipes 5, 10, 18 and 23 are 6 meters in lengthin the present example. Again, as described above, while theillustration of the system in FIGS. 1 and 2 show the compartments andtheir respective system components at different elevations, this is forpurposes of illustration only and in the example all similar systemcomponents for each respective stack A, B, C and D are at substantiallythe same respective elevation. Further, in the example hereof:

-   -   discharges from discharge sources 46, 48 and 50 are water closet        (abbreviated in the figures as “w.c.”) or toilet discharges to        stacks A, B and C and are over a period starting at 1 second and        extending to about 6 seconds, and a separate discharge from        discharge source 52 to stack D occurs at a period between 2 and        7 seconds;    -   a minimum water flow in each stack A, B, C and D continues        throughout the example, set at 0.1 liters per second, to        represent trailing water flowing through multiple appliance        discharges;        -   a stack base surcharge event is assumed to occur in stack A            at about 2.5 seconds; and    -   sequential sewer transients are imposed at the base of each        stack A, B, C and D in turn for a duration of 1.5 seconds during        the period beginning at 12 seconds and extending to 18 seconds.

It is believed that in this example in the system 32, the water flowswithin the network simulate actual system values, being representativeof current water closet discharge characteristics in terms of peak flowbeing about 2 liters per second, overall volume about 6 liters, andduration of discharge being about 6 seconds. The sewer transients in thepresent example are at 30 mm water gauge pressure, which arerepresentative but not excessive. Heights for the system stacks A, B, Cand D are measured in a positive manner upward from each stack base.Thus, entrained airflow towards the stack base is shown as a negativevalue, and airflow upward is shown as a positive value. Airflow enteringthe system 32 or 32A is therefore indicated with a negative value, andairflow exiting the system to the sewer 34 is indicated as a positivevalue, and airflow induced to flow up a stack will also have a positivevalue. Water downflow is indicated with a negative value.

Water Discharge to the System

-   -   Referring now to FIG. 5, the discharge sources 46, 48, 50 and 52        are illustrated as described above. FIG. 6 then illustrates the        measured air downflows which are established in pipes 1, 6 and        14 as expected. However, the entrained airflow in pipe 19 is        into the system 32 from the sewer 34. Initially, as there is        only the minimum flow, essentially a trickle, in pipe 19, the        initial entrained airflow in pipe 19 due to the discharge        sources 46, 48, 50 already being carried by pipes 1, 6 and 14,        is reversed, that is, up the stack D. This initial entrained        airflow in pipe 19 contributes to the entrained airflow demand        in pipes 1, 6 and 14. The AAV 70 connected to pipe 12 further        contributes to the entrained airflow demand, but initially this        is a small proportion of the required airflow and as seen in        FIG. 6. Further, the valve member 100 of the AAV 70 may flutter        in response to local pressure conditions. Following the        discharge source 52 discharge to stack D that establishes a        water downflow in pipe 19 from the time period at 2 seconds        onward, the reversed airflow initially established diminishes        due to the traction applied by the falling water film within the        pipe 19. However, the suction pressures developed in stacks A, B        and C still reults in a continuing but reduced reversed airflow        in pipe 19. As the water downflow in pipe 19 reaches its maximum        value from 3 seconds onward, the AAV 70 connected to pipe 12        opens fully and an increased airflow from this source may be        identified as shown in FIG. 6. The flutter activity of the valve        member 100 is replaced by a fully open period from 3.5 to 5.5        seconds.

FIG. 7 illustrates the air pressure profile starting from the stackbases 150 and 156 of stacks A and D, respectively upwardly to pipe 11,at about 2.5 seconds into the example hereof. The air pressure in stackD demonstrates a pressure gradient compatible with the reversed airflowmentioned above. The air pressure profile in stack A is typical for astack carrying an annular water downflow and demonstrates theestablishment of a positive backpressure due to the water curtain at thebase of the stack A. Following completion of the discharges of waterfrom discharge sources, the airflows will naturally attenuate over aperiod of time based on the frictional resistance in the system 32. As aminimum or trickle flow is assumed to continue in each stack, the rateof attenuation of the entrained airflows is low. The initial collapsedvolume of the PAPA 68 installed on pipe 13 was 0.4 liters, with a fullyexpanded volume of 40 liters. However, due to its relatively smallinitial volume it may be regarded as collapsed during the phase of theexample illustrated in FIG. 7.

Surcharge at the Base of Stack A

FIG. 8 shows a surcharge at the base 150 of stack A for pipe 1 at 2.5 to3 seconds. The entrained airflow in pipe 1 reduces to zero at the stackbase 150 and a pressure transient is generated within stack A asillustrated in FIG. 5. The impact of this transient will also be seenlater in a discussion of the trap seal responses for the system 32. Itwill also be seen from FIG. 8 that the predicted pressure at the bases150, 152, and 154 of stacks A, B and C at pipes 1, 6 and 14 conform tothat normally expected. That is to say, a small positive back pressureas the entrained air is forced through the water curtain at the base ofeach stack and into the sewer is shown. In the case of stack D, FIG. 6also shows the pressure at base 156 of stack D at pipe 19, with thereversed airflow drawn into the stack demonstrating a pressure drop asit traverses the water curtain present at that stack base 156.

Utilizing the AIRNET simulation practice allows the air pressureprofiles up stack A to be modeled during and following the surchargeillustrated in FIG. 8. FIGS. 9 and 10 illustrate the air pressureprofiles in stack A during the period of 2.5 to 3.0 seconds of theexample, the increasing and decreasing phases of the transientpropagation being presented sequentially. The traces illustrate thepropagation of the positive transient up the stack A as well as thepressure oscillations derived from the reflection of the transient atthe stack termination where the upper end of pipe 11 joins to the Tfitting 62.

Sewer Imposed Transients

FIG. 11 illustrates the imposition of a series of sequential sewertransients at the bases 150, 152, 154 and 156 of the pipes 1, 6, 14 and19 for each stack A, B, C and D, respectively. FIG. 12 demonstrates apattern that indicates the operation of both the PAPA 68 installed onpipe 13 and the self-venting within the system 32 provided by stackinterconnection.

As the positive pressure is imposed at the base 150 of pipe 1 at 12seconds, airflow is driven up stack A towards the PAPA 68 connection topipe 13. However, as the bases 152, 154 and 156 of the other stacks B, Cand D have not yet had positive sewer pressure levels imposed, asecondary airflow path is established downwards to the connections tosewer 34 at the bases 152, 154 and 156 in each of stacks B, C and D, asshown by the negative airflows in FIG. 12.

As the imposed transient abates, so the reversed flow reduces and thePAPA 68 discharges air to the system 32, again demonstrated by FIG. 12.This pattern repeats as each of the stacks is subjected to a sewertransient. Diversity implies that simultaneous sewer transientimposition would not be a likely condition and one that would beprudently avoided by ensuring connection to several sewer outlets (hereshown at bases 150, 152, 154 and 156). In a complex buildingarrangement, the provision of a plurality or multiplicity of suchconnections to the sewer 34 should not present an issue.

FIG. 13 illustrates a typical air pressure profile in stacks A and Bduring the sewer transient propagation in stack B at 15 seconds into theexample. The pressure gradient in stack B confirms that airflowdirection up the stack towards the T fitting 62 where pipes 12 and 13lead respectively to the AAV 70 and PAPA 68. It will be seen thatpressure continues to decrease down stack A until the pressure recoversin lower portions of the stack A at pipes 1 and 3. This is due to theeffect of the continuing waterflow in pipes 1 and 3.

The use of the PAPA 68 in the present example reacts to the sewertransients by absorbing airflow. The flexible reservoir 118 isexpandable and enables the PAPA 68 tp accumulate air inflow until itreaches its assumed 40 liter volume. At that point, the PAPA 68 willpressurize and will assist the airflow out of the network via the stackswhich are unaffected by the imposed positive sewer transient. As shownin FIG. 13, as the sewer transient is applied sequentially from stack Ato stack D, this pattern is repeated. The effective volume of the PAPA68, positioned at a relatively high level with respect to the system 32and the building 30, together with any other PAPAs 68 utilized in a morecomplex network than the system 32 shown in FIGS. 1 and 2, could beadapted to provide that virtually no system pressurization occurred.

FIG. 14 illustrates the airflow absorbed by the PAPA 68 during the sewertransient of the example hereof. The effect of sequential transients ineach of the stacks A, B, C and D is identifiable as the PAPA 68effective volume decreases between transients due to the entrainedairflow maintained by residual water flows in each stack.

Trap Seal Oscillation and Retention

The appliance traps 54, 56, 58 and 60 connected to the system 32 monitorand respond to the local branch air pressures. Utilizing the AIRNETsimulation, FIGS. 15, 16, 17 and 18 show the trap seal oscillations foreach respective trap for the four stacks A, B, C and D. It is to beunderstood that the term “trap seal” refers to the accumulated waterretained in each U-shaped trap to provide a barrier to resist theintroduction of gas or vapors from the stacks into the environment of acompartment or the building as a whole. The term “appliance side” inreference to the traps 54, 56, 58, and 60 refers to the side of the trapmore proximate the respective discharge source, while the term “systemside” in reference to the traps refers to the side of the trap moreproximate the junction of the respective feed pipe (2, 7, 15 and 20) toits corresponding wet stack discharge pipe (1, 6, 14 and 19).

FIG. 15, representing the trap seal at trap 54 of pipe 2, illustratesthe expected induced siphonage of trap seal water into the system 32 asthe stack pressure falls. The surcharge event in stack A interrupts thisprocess at the 2 second point of the example. The trap oscillationsabate following the cessation of water downflow in stack A. Theimposition of a sewer transient is apparent at the 12 second point ofthe example by the water surface level rising in the appliance ordischarge source side of the trap 54. A more severe transient could haveresulting in “bubbling through” the trap seal at this stage if the trapsystem side water surface level fell below −50 mm.

FIGS. 16 and 17 show the trap seal oscillations for the traps 56 and 58of pipes 7 and 15. FIGS. 16 and 17 are substantially identical to eachother until the sequential imposition of sewer transients at the 14 and16 second periods. As shown in FIGS. 16 and 17, the surcharge eventimposed for pipe 1 of stack A does not affect the traps 56 and 58 asthey are sufficiently remote from base 150 of stack A. As may be seen inFIG. 18, the trap 60 on pipe 20 displays a later initial reduction inpressure due to the delay in applied water downflow. The imposed sewertransient in pipe 19 is seen as it affects trap 60 at around 18 secondsinto the example.

As a result of the pressure transients arriving at each trap during theexample event hereof there will be a loss of trap seal water. Thisoverall effect results in each trap 54, 56, 58 and 60 displaying anindividual water seal retention that depends entirely on the usagewithin the system 32. FIG. 19 presents this data for the example hereoffor each of the traps 54, 56, 58 and 60. It may be noted that the traps56 and 58 for pipes 7 and 15 effectively were exposed to the same levelsof transient pressure despite the time difference in the arrival ofsewer transients.

The example of operation of the system 32 set forth above is believed tobe applicable also to system 32A. While the specific results may vary,the overall effect of maintaining trap seal integrity should be similar.This is because the arrangement of system 32A where the AAV 70 ispositioned in-line with the PAPA 68 with the PAPA 68 more proximate thedischarge sources and bases of the respective stacks, the AAV 70 willstill limit discharges of gas or vapors from the system 32A into theenvironment, with the PAPA 68 positioned to accumulate gas and thusabsorb pressure transients up the stack in communication with the AAV70.

It is believed that the foregoing example demonstrates that the systems32 and 32A will effectively function to provide a sealed buildingdrainage and ventilation system and that such is a viable option forcomplex buildings. As may be seen, the trap seal integrity may bemaintained during system operation experiencing both discharges from thedischarge sources and sewer imposed transients. Maintenance of trap sealintegrity is a primary component of limiting or avoiding systemcontamination from entering the building 30. The introduction of ambientair from the environment into the system 32 or 32A from AAV helps tomaintain trap seal integrity during discharges of water into the system32 or 32A, and system security may be further enhanced when the air sointroduced is provided from a controlled space or purification source.In addition, the placement of the PAPA 68 in parallel with the AAV 70,or alternatively in series with the AAV 70 remotely placed as shown inFIG. 2, allows the system 32 or 32A to maintain trap seal integrityduring pressure transients coming into the system from a sewer 34. Asealed building drainage and ventilation system 32 or 32A would providethe following advantages over existing systems:

-   -   system security would be immeasurably enhanced as all high-level        open system terminations would be redundant;    -   system complexity would be reduced while system predictability        would increase;    -   space and material savings would be provided during the        construction phase of any building installation, as the system        of the present invention utilizes both system diversity and the        use of AAV and PAPA devices to maintain trap seal integrity.

These benefits would thus preferably be provided by a system whichincorporates both active transient control and suppression into thedesign of the building's drainage and ventilation system, where airadmittance valves are used to suppress negative transients and variablevolume containment devices such as PAPAs are used to control positivetransients, with both most preferably positioned uppermost within thesystem within an enclosed loft or other secure space. Such a systemwould dramatically reduce the risk of building contamination due to theintroduction of chemical or biological agents as experienced, forexample, in the SARS spread mechanism within the Amoy Gardens complex inHong Kong in 2003. The diversity inherent in the operation of buildingdrainage and ventilation systems and the sewers connected to the systemhave a role in providing interconnected relief paths as part of thesystem of the present invention which provides an elegant and simplifiedsolution to such threats.

Although preferred forms of the invention have been described above, itis to be recognized that such disclosure is by way of illustration only,and should not be utilized in a limiting sense in interpreting the scopeof the present invention. Obvious modifications to the exemplaryembodiments, as hereinabove set forth, could be readily made by thoseskilled in the art without departing from the spirit of the presentinvention. For example, the invention hereof contemplates that thestacks need not be substantially vertically oriented but may also beinclined or otherwise positioned such that the base is positioned belowthe discharge sources and the connection of the stacks at the upperlevel of each is above the feed pipes. Further, several AAVs and PAPAsmay be used, so that there are several PAPAs and AAVs in parallel, orseveral connected PAPAs and AAVs as shown in FIG. 2 arranged inparallel. It may also be appreciated that the stacks may be anycombination or configuration of pipes, connectors, and other fittings,and each may include a plurality of discharge sources.

The inventor hereby states his intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of hisinvention as pertains to any apparatus not materially departing from butoutside the literal scope of the invention as set out in the followingclaims.

1. A drainage and ventilation system for a building comprising, incombination: a plurality of ventilation and drainage stacks, each ofsaid stacks having at least one wet stack portion adapted forfluidically connecting to a sewer, each of said stacks including a baseat a lower end for fluidically communicating with the sewer and a drystack portion positioned relatively above the wet stack pipe and thebase; at least one discharge source adapted for introducing liquid intothe at least one wet stack portion; at least one of said stacksincluding a feed pipe fluidically connecting said discharge source tosaid wet stack portion, said feed pipe including a trap; meansfluidically connecting each of said dry stack portions at an elevationabove the at least one discharge source; a positive air pressureattenuation device fluidically connected to said system; and an airadmittance valve fluidically connected to said system.
 2. A drainage andventilation system as set forth in claim 1, including a plurality ofdischarge sources, each of said stacks having at least one of saiddischarge sources fluidically connected to the respective wet stackportion.
 3. A drainage and ventilation system as set forth in claim 1,wherein said discharge source is selected from the group consisting ofwater closets, bidets, sinks and drains.
 4. A drainage and ventilationsystem as set forth in claim 1, including a connecting member forfluidically connecting said positive air pressure attenuation device andsaid air admittance device in parallel to said dry stack portionconnecting means.
 5. A drainage and ventilation system as set forth inclaim 1, wherein said positive air pressure attenuation device and saidair admittance valve are located in the ambient atmosphere.
 6. Adrainage and ventilation system as set forth in claim 1, wherein saidpositive air pressure attenuation device and said air admittance valveare located within an enclosed area.
 7. A drainage and ventilationsystem as set forth in claim 1, wherein the base of each of said stacksis connected to the sewer independent of the other stacks.
 8. A drainageand ventilation system as set forth in claim 1, where said trap has anappliance side positioned fluidically more proximate to said dischargesource and a system side positioned fluidically more proximate to therespective base of the stack.
 9. A drainage and ventilation system asset forth in claim 1, wherein said positive air pressure attenuationdevice and said air admittance valve are connected in series, with saidair admittance valve being fluidically remote from said positive airpressure attenuation device with respect to said stacks.
 10. A drainageand ventilation system as set forth in claim 1, wherein said positiveair pressure attenuation device and said air admittance valve arefluidically connected to said dry stack portion connecting means.
 11. Amethod of discharging liquid to a sewer, comprising the steps of:providing a ventilation and discharge system including a plurality ofstacks each having a base fluidically connected to the sewer, a wetstack portion and a dry stack portion, at least one of the stacks havinga source for discharging liquid to a respective one of the stacks and apipe for fluidically connecting to the wet stack portion, means forfluidically connecting the dry stack portions, an air admittance valvefluidically connected to said stacks, and a positive air pressureattenuation device fluidically connected to said stacks; deliveringliquid from the source to the sewer via the wet stack portion of said atleast one stack; accumulating air moving upwardly in at least one ofsaid stacks in said positive air pressure attenuation device; andintroducing air into at least one of said stacks through said airadmittance valve.
 12. A method as set forth in claim 11, wherein saidsystem includes a plurality of sources for discharging liquid into thesystem, including the step of delivering liquid from another one of saidplurality of sources to the sewer via one of the stacks.
 13. A method asset forth in claim 11, wherein said stacks are positioned substantiallyin the interior of a building, and wherein said air introduced into thesystem through the air admittance valve is drawn from the ambientatmosphere.
 14. A method as set forth in claim 11, wherein said stacksare positioned substantially in the interior of a building, and whereinsaid air introduced into the system through the air admittance valve isdrawn from an enclosed area.
 15. A method as set forth in claim 11,wherein said positive air pressure attenuation device and said airadmittance valve are positioned in parallel relationship such that airintroduced through the air admittance valve is delivered to theconnecting means without passing through the positive air pressureattenuation device.
 16. A method as set forth in claim 11, wherein saidpositive air pressure attenuation device is positioned fluidicallyintermediate the air admittance valve and the connecting means such thatthe step of introducing air into at least one of the stacks includespassing such air through the positive air pressure attenuation device.17. A method as set forth in claim 11, including the step of moving airfrom one of the stacks to another of the stacks through said connectingmeans in consequence of the delivery step.
 18. A method as set forth inclaim 11, wherein said air introduced into the system through the airadmittance valve is delivered to a dry stack portion of said pipe at anelevation above said wet stack portion.
 19. A method as set forth inclaim 11, wherein said accumulating air step includes receiving air intosaid positive air pressure attenuation device at a location which iselevated relative to said wet stack portion.